catalina.home和catalina.base
首先先看一下这两个参数在tomcat源码中的注释(参考类Globals)：
/**
* Name of the system property containing
* the tomcat product installation path
*/
public static final String CATALINA_HOME_PROP = "catalina.home";
/**
* Name of the system property containing
* the tomcat instance installation path
*/
public static final String CATALINA_BASE_PROP = "catalina.base";
就两个差异，一个是product，一个是instance。
再看一下RUNNING.txt中的说明
==================================================
Advanced Configuration - Multiple Tomcat Instances
==================================================
In many circumstances, it is desirable to have a single copy of a Tomcat
binary distribution shared among multiple users on the same server. To make
this possible, you can set the CATALINA_BASE environment variable to the
directory that contains the files for your 'personal' Tomcat instance.
When running with a separate CATALINA_HOME and CATALINA_BASE, the files
and directories are split as following:
In CATALINA_BASE:
* bin - Only the following files:
* setenv.sh (*nix) or setenv.bat (Windows),
* tomcat-juli.jar
The setenv scripts were described above. The tomcat-juli library
is documented in the Logging chapter in the User Guide.
* conf - Server configuration files (including server.xml)
* lib - Libraries and classes, as explained below
* logs - Log and output files
* webapps - Automatically loaded web applications
* work - Temporary working directories for web applications
* temp - Directory used by the JVM for temporary files (java.io.tmpdir)
In CATALINA_HOME:
* bin - Startup and shutdown scripts
The following files will be used only if they are absent in
CATALINA_BASE/bin:
setenv.sh (*nix), setenv.bat (Windows), tomcat-juli.jar
* lib - Libraries and classes, as explained below
* endorsed - Libraries that override standard "Endorsed Standards"
libraries provided by JRE. See Classloading documentation
in the User Guide for details.
By default this "endorsed" directory is absent.
大概意思就是
CATALINA_BASE：是实例配置位置，也就是一个tomcat可以配置多个实例，实例里面有自己的配置CATALINA_HOME：是tomcat安装位置
tomcat内部设置
1.从入口org.apache.catalina.startup.main方法开始跟踪，
Bootstrap bootstrap = new Bootstrap();
try {
bootstrap.init();
} catch (Throwable t) {
handleThrowable(t);
t.printStackTrace();
return;
}
daemon = bootstrap;
这是tomcat7第一次启动时最先执行的代码。
2.进入init，就是一堆初始化了，最先执行的
// Set Catalina path
setCatalinaHome();
setCatalinaBase();
3.进入setCatalinaHome()
if (System.getProperty(Globals.CATALINA_HOME_PROP) != null)
return;
File bootstrapJar =
new File(System.getProperty("user.dir"), "bootstrap.jar");
if (bootstrapJar.exists()) {
try {
System.setProperty
(Globals.CATALINA_HOME_PROP,
(new File(System.getProperty("user.dir"), ".."))
.getCanonicalPath());
} catch (Exception e) {
// Ignore
System.setProperty(Globals.CATALINA_HOME_PROP,
System.getProperty("user.dir"));
}
} else {
System.setProperty(Globals.CATALINA_HOME_PROP,
System.getProperty("user.dir"));
}
它的步骤是：
1.从system中取，如果有就直接返回。
2.如果bootstrap.jar在当前工作目录，就取上一级，返回。
3.如果bootstrap.jar没有在当前工作目录，那么就设置
CATALINA_HOME为当前工作目录
4.进入setCatalinaBase()
if (System.getProperty(Globals.CATALINA_BASE_PROP) != null)
return;
if (System.getProperty(Globals.CATALINA_HOME_PROP) != null)
System.setProperty(Globals.CATALINA_BASE_PROP,
System.getProperty(Globals.CATALINA_HOME_PROP));
else
System.setProperty(Globals.CATALINA_BASE_PROP,
System.getProperty("user.dir"));
它的步骤是：
1.从system中取，如果有就直接返回。
2.如果已经设置了
CATALINA_HOME，就设置CATALINA_BASE为CATALINA_HOME，返回。3.设置
CATALINA_BASE为当前工作目录
总结
1.如果我们安装的tomcat就只有一个实例，就只需要配置CATALINA_HOME
2.有时候项目太多，它们相互之间的一些配置又有些不同，我们就可以考虑用多个实例，而不必去复制多个tomcat了。实例配置了之后，在启动时只需要指定CATALINA_BASE就可以了
